linux-kernel - [RFC PATCH 6/7] events: Create an trace_get_context

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Date:   Tue,  2 Apr 2019 22:03:58 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Romulo Silva de Oliveira <romulo.deoliveira@...c.br>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: [RFC PATCH 6/7] events: Create an trace_get_context_bit()

Create a specific function to get the current task context.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>
Cc: Romulo Silva de Oliveira <romulo.deoliveira@...c.br>
Cc: Clark Williams <williams@...hat.com>
Cc: linux-kernel@...r.kernel.org
Cc: x86@...nel.org
---
 kernel/events/internal.h | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 79c47076700a..241a2318bfdc 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -202,18 +202,37 @@ arch_perf_out_copy_user(void *dst, const void *src, unsigned long n)
 
 DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
 
-static inline int get_recursion_context(int *recursion)
+/*
+ * Used for which event context the event is in.
+ *  NMI     = 0
+ *  IRQ     = 1
+ *  SOFTIRQ = 2
+ *  NORMAL  = 3
+ *
+ * See trace_recursive_lock() comment for more details.
+ */
+enum {
+	TRACE_CTX_NMI,
+	TRACE_CTX_IRQ,
+	TRACE_CTX_SOFTIRQ,
+	TRACE_CTX_NORMAL,
+	TRACE_CTX_MAX
+};
+
+static __always_inline int trace_get_context_bit(void)
 {
-	int rctx;
+	unsigned long pc = preempt_count();
 
-	if (unlikely(in_nmi()))
-		rctx = 3;
-	else if (in_irq())
-		rctx = 2;
-	else if (in_softirq())
-		rctx = 1;
+	if (pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))
+		return pc & NMI_MASK ? TRACE_CTX_NMI :
+			pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ;
 	else
-		rctx = 0;
+		return TRACE_CTX_NORMAL;
+}
+
+static inline int get_recursion_context(int *recursion)
+{
+	int rctx = trace_get_context_bit();
 
 	if (recursion[rctx])
 		return -1;
-- 
2.20.1